1. Field of the Invention
The present invention relates to a method of manufacturing a thin film magnetic head having at least an inductive magnetic transducer for writing.
2. Description of the Related Art
In recent years, an improvement in performance of a thin film magnetic head is demanded in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
In order to improve the recording density in the performances of the recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring to FIGS. 31 and 36, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in FIG. 31, an insulating layer 102 made of, for example, aluminium oxide (Al2O3; hereinbelow, simply called xe2x80x9caluminaxe2x80x9d) is deposited in a thickness of about 5.0 to 10.0 xcexcm on a substrate 101 made of altic (Al2O3.TiC) or the like. Subsequently, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. For example, alumina layer is then sputter-deposited in a thickness of 100 to 200 nm on the bottom shield layer 103 to form a shield gap film 104. An MR film 105 for constructing an MR device for reproducing is deposited in a thickness of tens nm on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then lead layers (not shown) as lead electrode layers, which are electrically connected to the MR film 105, are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104, and the MR film 105, and the MR film 105 is buried in the shield gap films 104 and 106. A top shield-cum-bottom pole (hereinbelow, referred to as a bottom pole) 107 made of a magnetic material such as nickel iron alloy (NiFe; hereinbelow, also simply called xe2x80x9cPermalloy (trade name)xe2x80x9d) used for both of the reproducing head and the recording head is formed on the shield gap film 106.
As shown in FIG. 32, on the bottom pole 107, a write gap layer 108 made of an insulating material such as alumina is formed. Further, a photoresist film 109 is formed in a predetermined pattern on the write gap layer 108 by high-precision photolithography. On the photoresist film 109, a thin film coil 110 for an inductive-type recording head made of, for example, copper (Cu) is formed by plating or the like. A photoresist film 111 is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist film 109 and the thin film coil 110. In order to insulate the winding portions of the thin film coil 110 from each other, a heat treatment is conducted at, for example, 250 degrees on the photoresist film 111.
As shown in FIG. 33, in a position rearward of the thin film coil 110 (the right side in FIG. 33), an opening 108a is formed by partially etching the write gap layer 108 in order to form a magnetic path, thereby exposing part of the bottom pole 107. A top yoke-cum-top pole (hereinbelow, called top pole) 112 made of a magnetic material having high saturated magnetic flux density such as Permalloy is selectively formed so as to cover the exposed face of the bottom pole 107, the photoresist film 111 and the write gap layer 108.
As a method of forming the top pole 112, for example, as disclosed in Japanese Unexamined Patent Application No. Hei 7-262519, a frame plating is used. When the top pole 112 is formed by using the frame plating, first, on the whole coil portion (hereinbelow, called an xe2x80x9capex portionxe2x80x9d) projected like a mountain covered with the photoresist film 111, a thin electrode film made of, for example, Permalloy is deposited by sputtering or the like. A photoresist is then applied on the electrode film, thereby forming the photoresist film. The photoresist film is patterned by a photolithography to form a frame (outer frame) for a plating. Then the electrode film formed before is used as a seed layer and a plating film made of Permalloy is grown by plating, thereby forming the top pole 112.
The top pole 112 has, for example, a shape in plane as shown in FIG. 36 which will be described hereinlater and includes a yoke part 112a and a pole tip part 112b. The top pole 112 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108a. Subsequently, by using part (pole tip part 112b) of the top pole 112 as a mask, both the write gap layer 108 and bottom pole 107 are selectively etched about 0.5 xcexcm by ion milling (refer to FIG. 35) and, after that, an overcoat layer 113 made of, for example, alumina is formed on the top pole 112. Finally, by machining and polishing, the track surface, that is, an air bearing surface 120 of the recording head and reproducing head is formed, thereby completing a thin film magnetic head.
FIGS. 34 to 36 show the structure of the thin film magnetic head in a completed state. FIG. 34 is a cross section of the thin film magnetic head in the direction perpendicular to the air bearing surface 120. FIG. 35 is an enlarged cross section in the direction parallel to the air bearing surface 120 of the pole part. FIG. 36 is a plan view of the structure. FIG. 33 is a cross section taken along line XXXIIIxe2x80x94XXXIII of FIG. 36. In FIGS. 34 to 36, the overcoat layer 113 and the like are omitted. In FIG. 36, with respect to the thin film coil 110 and the photoresist film 111, only their outlines are shown.
In FIGS. 34 and 36, xe2x80x9cTHxe2x80x9d denotes the throat height and xe2x80x9cMRHxe2x80x9d indicates the MR height. The xe2x80x9cthroat height (TH)xe2x80x9d is one of factors which determine the performance of the recording head and is length from the position of the edge on the side closest to the air bearing surface 120 of the insulating layer (photoresist film 111) for electrically isolating the thin film coil 110 from the other conductive portions, that is, from the throat height zero position (THO) to the air bearing surface 120. In order to improve the performance of the recording head, it is necessary to optimize the throat height (TH). The throat height (TH) is controlled by a polishing amount at the time of forming the air bearing surface 120. The xe2x80x9cMR height (MRH)xe2x80x9d denotes length from the position of the edge on the side furthest from the air bearing surface 120 of the MR film 105, that is, the MR height zero position (MRH0) to the position of the air bearing surface 120. The MR height (MRH) is also controlled by the polishing amount at the time of forming the air bearing surface 120.
Besides the throat height (TH) and the MR height (MRH), another factor which determines the performance of the thin film magnetic head is an apex angle (xcex8) shown in FIG. 34. The apex angle xcex8 is an average inclination angle of an inclined face close to the air bearing surface 120 of the photoresist film 111.
As shown in FIG. 35, a structure such that part of the write gap layer 108 and part of the bottom pole 107 are etched in a self aligned manner to the pole tip part 112b of the top pole 112 is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. xe2x80x9cP2Wxe2x80x9d in the drawing indicates the width of the portion having the trim structure (hereinbelow, simply called xe2x80x9cpole part 500xe2x80x9d), that is, the pole width (hereinbelow, also called xe2x80x9ctrack widthxe2x80x9d). The processing dimension of the pole width P2W depends on the width of a portion corresponding to the pole part 500 in a mask (photoresist film pattern in the above case) used at the time of performing an etching process to form the trim structure. xe2x80x9cP2Lxe2x80x9d in the drawing denotes the thickness of the pole tip part 112b as part of the pole part 500, that is, the pole length. As shown in FIG. 35, lead layers 121 as lead electrode layer electrically connected to the MR film 105 are provided on both sides of the MR film 105. In FIGS. 31 to 34, the lead layer 121 is omitted.
As shown in FIG. 36, the top pole 112 has the yoke part 112a, which occupies a major part of the top pole 112, and the pole tip part 112b having an almost constant width as the pole width P2W. In the connecting portion between the yoke part 112a and the pole tip part 112b, the outer edge of the yoke part 112a forms an angle xcex1 to a plane parallel to the air bearing surface 120. In the connecting portion, the outer edge of the pole tip part 112b and a plane parallel to the air bearing surface 120 form an angle xcex2. For example, xcex1 is 45 degrees and xcex2 is 90 degrees. As described above, the pole tip part 112b is a part serving as a mask used to form the trim structure of the pole part 500. As understood from FIGS. 34 and 36, the pole tip part 112b extends on the flat write gap layer 108 and the yoke part 112a extends on the apex portion.
Detailed structural characteristics of the top pole are described in, for example, Japanese Unexamined Patent Application No. Hei 8-249614.
In the conventional thin film magnetic head having the structure as shown in FIG. 33, the magnetic flux generated by the thin film coil 110 at the time of recording information propagates through the top pole 112 from the yoke part 112a toward the pole tip part 112b and finally reaches the tip of the pole tip part 112b. The magnetic flux reached the pole tip part 112b generates a signal magnetic field to the outside. By the signal magnetic field, information is recorded onto a recording medium (not shown).
In order to assure the excellent overwrite characteristics of the thin film magnetic head, generally, it is necessary to smoothly and sufficiently supply the magnetic flux to the pole tip part 112b of the top pole 112 to sufficiently generate the signal magnetic field.
In the conventional thin film magnetic head shown in FIG. 33, however, only the thin write gap layer 108 is provided between the pole tip part 112b of the top pole 112 and the bottom pole 107. Part of the magnetic flux flowed from the yoke part 112a toward the pole tip part 112b does not therefore reach the tip of the pole tip part 112b but passes through the write gap layer 108 and propagates to the bottom pole 107. In the following, the propagation of the magnetic flux from the top pole 112 to the bottom pole 107 via the write gap layer 108 will be called xe2x80x9cleakage of magnetic fluxxe2x80x9d. Such a tendency is conspicuous in a region 112S defined between a region formed on the flat write gap layer 108 in the top pole 112 and a region formed on the apex because a downward flow of the magnetic flux in the top pole 112 occurs in the region 112S extending in the thickness direction (longitudinal direction in the drawing).
The xe2x80x9cleakage of the magnetic fluxxe2x80x9d induces inconveniences as described below.
1) Due to the leakage of the magnetic flux from the top pole 112 to the bottom pole 107, the absolute volume of the magnetic flux propagating through the top pole 112 from the yoke part 112a to the pole tip part 112b decreases. In such a case, the magnetic flux generated by the thin film coil 110 cannot be sufficiently supplied to the tip of the pole tip part 112b. Consequently, the overwrite characteristic of the thin film magnetic head deteriorates severely.
2) Local concentration of the magnetic flux on the bottom pole 107 due to the leakage of the magnetic flux exerts an adverse influence on the reading operation of the thin film magnetic head. For example, when the magnetic flux concentrates on the bottom pole 107 more than necessary and part of the magnetic flux passes through the bottom pole 107 and reaches the MR film 105, the magnetic flux reached the MR film 105 acts as magnetic noises at the time of the reading operation of the reproducing head. Due to this, the normal reading operation of the thin film magnetic head is disturbed.
The invention has been achieved in consideration of the problems. An object is to provide a thin film magnetic head capable of obtaining a sufficient overwrite characteristic by suppressing xe2x80x9cleakage of magnetic fluxxe2x80x9d in a propagation process of magnetic flux and a method of manufacturing the same.
According to the invention, there is provided a thin film magnetic head comprising: a first magnetic layer having a magnetic pole and a second magnetic layer having a magnetic pole, which are magnetically coupled to each other, the magnetic poles facing each other with a gap layer having a flat surface region in between in part of a side of a recording-medium-facing surface facing a recording medium, and the first magnetic layer including a first magnetic portion having a constant width portion which extends from the recording medium facing surface in a length direction so as to be apart from the recording medium facing surface and which specifies a recording track width of the recording medium; a thin film coil part disposed between the two magnetic layers sandwiching an insulating layer; and a first non-magnetic pattern which is embedded in a recess formed in part on the side in contact with the gap layer, of the second magnetic layer, and which serves as part of the insulating layer, the position of the front end of the first non-magnetic pattern specifying the position of the front end of the insulating layer, wherein the front end of the first non-magnetic pattern is positioned in a region where the constant width portion extends of the region where the first magnetic portion extends.
According to the invention, there is provided a method of manufacturing a thin film magnetic head comprising: a first magnetic layer having a magnetic pole and a second magnetic layer having a magnetic pole, which are magnetically coupled to each other, the magnetic poles facing each other with a gap layer having a flat surface region in between in part of a side of a recording-medium-facing surface facing a recording medium, and the first magnetic layer including a first magnetic portion having a constant width portion which extends from the recording medium facing surface in a length direction so as to be apart from the recording medium facing surface and which specifies a recording track width of the recording medium; and a thin film coil part disposed between the two magnetic layers sandwiching an insulating layer; wherein the method comprises a step of forming a first non-magnetic pattern serving as part of the insulating layer in a recess formed in part on the side in contact with the gap layer, of the second magnetic layer, so that the front end of the first non-magnetic pattern is positioned in a region where the constant width portion extends of the region where the first magnetic portion extends, and specifies the position of the front end of the insulating layer.
In the thin film magnetic head of the invention, the position of the front end of the insulating layer is specified by the position of the front end of the first non-magnetic pattern as part of the insulating layer. In this case, the xe2x80x9cposition of the front end of the insulating layerxe2x80x9d is a position of one of the edges of the insulating layer, which is the closest to the recording medium facing surface. Especially, due to the existence of the first non-magnetic pattern, propagation of the magnetic flux from its upper region to its lower region can be suppressed.
In the thin film magnetic head or in the method of manufacturing the head of the invention, further, a second non-magnetic pattern which serves as part of the insulating layer so as to extend in contact with a side of the gap layer opposite to the side with which the first non-magnetic pattern is in contact may be provided.
In the thin film magnetic head of the invention, the surface near the front end of the second non-magnetic pattern is inclined with respect to the surface of the gap layer.
In the thin film magnetic head of the invention, the position of the front end of the second non-magnetic pattern is rearward in the length direction of the position of the front end of the first non-magnetic pattern, and the first magnetic portion may extend from a flat region of the gap layer to the inclined face of the second non-magnetic pattern.
In the method of manufacturing the thin film magnetic head of the invention, the second non-magnetic pattern may be formed so that the front end of the second non-magnetic pattern is positioned rearward of the front end of the first non-magnetic pattern along the length direction.
In the thin film magnetic head or the method of manufacturing the head of the invention, at least the constant width portion in the first magnetic portion may extend on the flat region of the gap layer.
In the thin film magnetic head or the method of manufacturing the head of the invention, the first magnetic portion may further comprise: at least two connection portions disposed so as to be separated from each other in the track width direction; and a coupling portion for magnetically coupling the constant width portion and at least two connection portions. In such a case, part of the insulating layer may be buried in a region surrounded by the coupling portion in the first magnetic portion and at least two connection portions.
According to the method of manufacturing the thin film magnetic head of the invention, in the case where the surface near the front end of the second non-magnetic pattern has an inclined face inclined with respect to the surface of the gap layer and at least part of the coupling portion in the first magnetic portion and the connection portion is disposed on the inclined face of the second non-magnetic pattern, the step of forming the first magnetic portion may include: a step of forming a photoresist layer so as to cover at least the flat region in the gap layer and the inclined region in the second non-magnetic pattern; a first exposing step of selectively exposing a first region including a region corresponding to the shape in plane of the constant width portion, in the photoresist layer of the flat region in the gap layer; a second exposing step of selectively exposing a second region corresponding to the shape in plane of at least the coupling portion and the connection portion of the photoresist layer in a region extending from the inclined region of the second non-magnetic pattern to the flat region of the gap layer; a step of forming a photoresist pattern by developing both the first and second regions of the photoresist layer in a lump; and a step of integrally forming the constant width portion, the coupling portion and the connection portion by using the photoresist pattern. In such a case, in the second exposing step, preferably, the first and second regions are partially overlapped with each other.
In the thin film magnetic head or the method of manufacturing the head of the invention, the first magnetic layer may further include: a second magnetic portion which is magnetically coupled to the first magnetic portion so as to be partially overlapped with each other; and a third magnetic portion for magnetically coupling the second magnetic portion to the second magnetic layer.
The method of manufacturing the thin film magnetic head of the invention may further include the steps of: forming the first magnetic portion and, simultaneously, forming the third magnetic portion and a coil connection pattern as part of the thin film coil part on a coil end provided at the end of the thin film coil part; forming a coil covering layer as part of the insulating layer so as to cover at least the first magnetic portion, the third magnetic portion and the coil connection pattern; planarizing the surface of the coil covering layer by polishing until at least the first magnetic portion, the third magnetic portion and the coil connection pattern are exposed; and forming the second magnetic portion so as to be magnetically coupled with the exposed faces of both the first and third magnetic portions on the surface planarized by the polishing and, simultaneously, forming a conductive layer pattern so as to be electrically connected to the exposed face of the coil connection pattern.
In the thin film magnetic head or the method of manufacturing the head of the invention, at least one of the first and second magnetic layers may be made of a material containing either nickel iron alloy or iron nitride, or a material containing an amorphous alloy. It is preferable to use either cobalt iron alloy or zirconium cobalt iron alloy as the amorphous alloy.
Other and further objects, features and advantages of the invention will appear more fully from the following description.